1. Field
The present disclosure relates to an accelerator device to output a signal based on a rotation angle of a grip which is disposed at a handlebar being repeatedly-rotatable from a predetermined original point position about an axis center of the handlebar.
2. Description of the Related Art
In a vehicle having handlebars as an operating device for a motorcycle etc. and having a drive device such as an engine, a grip for performing acceleration operation is disposed to a handlebar section.
In the related art, a grip which is approximately cylinder-shaped is rotatably placed at an end part of a handlebar in a state of being externally fitted to the end part. Using the grip, it is possible to vary opening of a throttle valve with a rotation amount (i.e., a rotation angle) of the grip.
Traditionally, a grip and a throttle valve have been interlocked with a wire, for example. Recently, a fuel injection device has been also utilized for a motorcycle instead of a carburetor. Accordingly, control of throttle valve opening and control of fuel injection amount with a fuel injection device based on a signal has been performed as measuring a rotation angle of a grip and outputting the measured rotation angle as the signal.
Rotation angle detecting means which detects increase and decrease of the rotation angle (i.e., the rotation amount) of the grip is disposed to the grip, so that the signal corresponding to the rotation angle of the grip is outputted.
When the grip is operated in one rotation direction with an operator's hand, the rotation angle detecting means detects increase of the rotation angle in the one rotation direction. Then, the signal indicating the increase of the rotation angle is outputted to a control unit, so that control is performed to increase opening of the throttle valve, for example.
In contrast, when the operator rotates the grip rotated in the one rotation direction to return in the other rotation direction or the grip is rotated to return in the other rotation direction by urging means connected to the grip with releasing of the operator, the rotation angle detecting means detects decrease of the rotation angle in the one rotation direction. Then, the signal indicating the decrease of the rotation angle is outputted to the control unit, so that control is performed to decrease opening of the throttle valve, for example.
Here, for example, the rotation angle detecting means to detect the rotation angle of the grip may be a potentiometer or may be constituted with a magnet which is rotated with the grip and a detection element to detect a magnetic field (i.e., variation of a magnetic field) such as a Hall element and a magnetoresistance element.
In essence, such an accelerator device is provided with the grip, the rotation angle detecting means which detects the rotation angle of the grip as described above, and the urging means which urges the grip to return toward an original point.
For example, in such an accelerator device, an arc-shaped sector gear which corresponds to a rotation range being less than one turn of the grip is disposed to the grip. A gear of which diameter is smaller than the grip is engaged with the sector gear as being interlocked. Then, a potentiometer is disposed to one side face side of the gear as the rotation angle detecting means being coaxial with the gear. Further, there has been proposed to dispose urging means for returning toward an original point position respectively to both of the gear and the grip. For example, see Japanese Patent Publication No. 2002-264876. Here, in the above example, the urging means at the gear side is disposed to the gear at the potentiometer side.
There has also been disclosed another example including a sector gear which is arranged in an arc shape along the circumferential direction of a grip at a base end side of the grip, a detected body having a magnet as being formed in an arc shape to be overlapped with the sector gear at a position being shifted against the sector gear in the axial direction of the grip, a detection element which detects magnetic field variation of the detected body caused by rotation of the grip, and urging means for returning to an original point disposed to the gear. For example, see Japanese Patent Publication No. 2008-162420.
Further, there has been proposed another example in which a roller which is integrally rotated with a grip as being placed coaxially therewith is disposed to the grip, a rotary body being adjacent to the roller is to be rotated as being interlocked with the grip by arranging mutually-engaging gears respectively around the roller and the rotary body, a north-pole and a south-pole of a magnet are disposed to the rotary body, and urging means is disposed to the grip. For example, see Japanese Patent Publication No. 2005-041259.
In this example, a magnetoresistance element is utilized for detecting magnetic field variation due to magnet movement. Then, a concave portion to which a convex portion of the center of the rotary body is inserted is disposed to the case, so that the rotary body is rotatably supported by the case. Further, the magnetoresistance element is fixed to the cover which covers an opening of the case as being opposed to the case.
In the above examples, the urging means adopts a torsion coil spring and the like, for example.
When the urging means is disposed to the grip as disclosed in Japanese Patent Publication No. 2002-264876 and Japanese Patent Publication No. 2008-162420, the torsion coil spring is arranged at the outside of the handlebar because an end part of the handlebar is placed at the inside of the grip. Accordingly, the spring diameter becomes large, so that miniaturization of the accelerator device is difficult to obtain.
Further, in a case that the magnet is disposed to the grip as the detected body for the rotation angle detecting means, the magnet rotatably moved along with the grip is required to be placed at the outside from the outer circumference of the handlebar. Accordingly, the outer diameter of the accelerator device is enlarged.
Here, since the rotation angle of the grip for accelerator operation is not so large, the magnet is required to be large in order to enlarge a magnetic variation amount due to magnetic rotational movement to be detected by the detecting body. As a result of the above, when the magnet for detecting the rotation angle is disposed to the grip side, miniaturization of the accelerator device is difficult to obtain.
Further, in the structure that magnetic field variation due to rotational movement of the magnet as described in Japanese Patent Publication No. 2008-162420 and Japanese Patent Publication No. 2005-041259, when the magnet is disposed to the grip and the detection element is fixed to a case, cover or the like which is fixed to the handlebar, there is a possibility that the magnet disposed to the grip is moved in the axial direction of the grip along with the grip against the detection element owing to clearance between the grip and the case or the cover which restricts the axial position of the grip, deformation of these components, and the like. In this case, the magnet is moved in the axial direction of the grip against the detection element.
In a case that the magnet is moved in the axial direction against the detection element, output of the detection element is shifted compared to a case that the magnet is moved only rotationally against the detection element. Accordingly, detection accuracy of the rotation angle of the grip is worsened.
Further, in Japanese Patent Publication No. 2005-041259, the magnet is disposed not to the grip but to the rotary body and the detection element is hold by the cover. Accordingly, when an impact and external force are applied to the grip during travelling, the rotary body having the magnet is moved in the direction other than the rotation direction as a result of clearance variation at a section which rotatably holds the rotary body, deformation of the case and cover, and the like. Accordingly, output of the detection element is varied.
To address the above issues, the present disclosure provides an accelerator device capable of improving detection accuracy of a rotation angle of a grip while achieving miniaturization.